The present invention relates a hybrid drive system constructed by an internal combustion engine and a hybrid transmission including a differential mechanism and two motor/generators, and more particularly to a shift control system which appropriately executes a shift control of the hybrid transmission so as not to generate a strange acceleration/deceleration or an exceeding engine revolution due to an unnatural change of a driving torque or transmission ratio.
It is known that a hybrid transmission is generally constructed by relationally connecting an internal combustion engine, an output shaft, two motor/generators and a differential mechanism to execute a shifting through the control of the two motor/generators. Such a hybrid transmission is arranged to drive the motor/generators using electric power of a battery. Accordingly, it is necessary to limit the electric power used for the motor/generators at a value smaller than a rated electric power of the battery as is similar to the limitation of an electric device installed in a vehicle.
Japanese Published Patent Application No. 2002-058113 discloses a power control method of the motor/generators for a hybrid vehicle. More specifically, the power control method is basically applied to a power output system which comprises at least an electric device operated according to charging/discharging of a battery, and corrects a target output of the electric device at a value which requires a power smaller than a rated momentary electric power of the battery when the electric device outputs the target output requiring a power greater than the rated momentary electric power.